I would like being able to see the very content of the tab which it had when I last looked at it.
The tab should only update after a manual reload, neither in the background nor at startup.

Like Ayespy, I think OP (ricardit0) meant he didn't want all the previously open tabs to be re-opened when restarting Vivaldi, but your take on it could be correct. If so, Olde Opera (12.x and earlier) cache management was really quite remarkable in many ways, including (usually) what you're talking about with the cached content being reused when Opera was re-opened.

I don't think Vivaldi's cache management is there yet, and I don't know if that is one of the developers' goals. But if that is a feature you want, you might also post it in the official Vivaldi Feature Request thread.